(1) Field of the Invention
The present invention relates to a ceramic coating containing dispersion strengthened rare earth stabilized zirconia to be applied to a turbine engine component and a method for forming such a coating.
(2) Prior Art
Ceramic thermal barrier coatings have been used for decades to extend the life of combustors and high turbine stationary and rotating components. Zirconia has typically been the base ceramic. Stabilizers have been added to prevent the deleterious phase transformation to the monoclinic phase from the high temperature stable cubic or tetragonal phase. Early stabilizers such as 22 wt % magnesia were utilized, but as turbine temperatures increased beyond 1900 degrees Fahrenheit, the durability of the magnesia stabilized zirconia deteriorated since magnesia stabilized zirconia crystallographically destabilizes above 1750 degrees Fahrenheit. Compositional improvements led to a 7 wt % yttria stabilized zirconia. With this composition, thermal barrier coatings attained a good balance between durability, i.e. thermal oxidative cycling; stability, i.e. sintering and phase stability; mechanical properties, i.e. fracture toughness, erosion resistance and adherence; and thermal properties, i.e. thermal conductivity and thermal expansion.
As current engine models continue to increase temperatures and warrant decreased component weight, advanced ceramics are being pursued. A zirconia based coating, such as a gadolinia-zirconia coating as described in commonly owned U.S. Pat. No. 6,177,200 has been developed which provides a reduced thermal conductivity ceramic thermal barrier coating. However, such coating would benefit from improved mechanical properties, such as fracture toughness and erosion resistance.